China's capital Beijing raised its four-tiered alert system to orange for the first time this week, after being criticized by local media for failing to act against high pollution levels last week, according to Reuters.

In order to issue a red alert, which is the highest level that can been issued, Beijing's alert system requires a forecast of three days in a row of severe pollution. Extreme pollution or polluted skies are expected to clear in under three days, according to the Associated Press.

By issuing an orange alert, schools and kindergartens are advised to cancel outside sports events, but schools can remain open.

Government vehicles are also allowed to remain on the road, unless a red level is issued eventually.

News agency Xinhua confirmed in a report that the city had dispatched inspectors to nearby plants around the capital to warn those found breaching emission rules would be fined.

Any level above 300 is considered "hazardous" by the U.S. Environmental Protection Agency. Late last week, levels topped 500, according to Reuters.

Local forecasters have said the smog may continue for around three days and authorities have pleaded with residents to avoid using their cars for the time being.

"Yesterday, I thought it was bad enough when I went out to eat. But this morning I was hacking," a Beijing pedestrian who gave her name as Li said, according to AP.

Locals have been advised to use public transportation, and to turn their vehicles off rather than let them run idle. Officials are also calling for water sprinkling on streets and dust-control measures at building sites, according to AP.

If a red alert is issued, approximately half of Beijing's 5 million cars will be asked to stay off the road.

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